The invention relates to a means and method for determining susceptibility of a device to radiated energy, and more particularly to a means and method utilizing a stripline unit for applying radiated energy to a device or measuring the leakage of energy from the device under test.
Since many devices, such as electronic equipment and electromechanical apparatus are susceptible to electromagnetic radiation and may also emit radiation, testing means for determining such susceptibility to radiation and emission of radiation have been utilized. In order to determine the susceptibility of a device to radiation, it must be subjected to field strengths which are representative of the environment in which it will be operated. For testing purposes, the test fields to which such devices are subjected should be determinable to a high degree of certainty. It is therefore desirable that such fields be uniform and well behaved so that the level of radiation to which the equipment is subject can be accurately determined.
In order to achieve such conditions, devices have been subjected to radiation inside of shielded or screened enclosures where good electrical isolation is obtained from external radiation. Even with such shielded enclosures, serious measurement problems and errors can result due to the high conductivity and reflectivity of the enclosure walls which set up standing waves which may interfere with the signals being measured. Such conditions have been considered in the article by Myron L. Crawford entitled Techniques For Measurement Of Electromagnetic Radiation And Susceptibility Of Electronic Equipment in EMCMON 1975, pages 38-44.
In order to avoid such reflecting surfaces underground rooms or tunnels have been used as test chambers for measurements at frequencies of about a few megahertz since the non-metallic, lossy, and irregular walls of low reflectivity, reduce reflections and antenuate the transmitted or received energy. Another technique utilizes a transverse electromagnetic transmission (TEM) cell at frequencies below a few hundred megahertz in which the device under test is placed wholly within the cell. The cell acts as a shielded enclosure providing the desired electrical isolation and provides a known uniform transverse electromagnetic field within it for susceptibility testing of the equipment. However, since the equipment must be placed entirely within the cell, the size of the equipment under test must be limited and the upper frequency limit for the transmitted wave is considerably reduced as a function of the cell size.
The test methods presently being used are also exemplified by the specifications in Measurement of Military Standard Electromagnetic Interference Characteristics, July 31, 1967, MIL-STD-462, Methods RS01, RS02, RS03 (Radiated Susceptibility). Such specified tests require high powered generators to provide the representative field strengths, and the fields generated are perturbed by reflections from the shielded enclosures. The parallel stripline described in MIL-STD-462, also severely limits the size of the equipment which can be tested.